Layout of magnetoresistance element

Bridges typically include four or more magnetoresistance elements. Magnetoresistance elements in a bridge may include tunnel magnetoresistance (TMR) elements. Each TMR element may include a plurality of pillars. Generally, in fabricating bridges, pillars of each TMR element are grouped together on a die in a location separate from the pillars of the other TMR elements.

In one aspect, a bridge includes a first magnetoresistance element that includes a first set of pillars, a second magnetoresistance element that includes a second set of pillars, a third magnetoresistance element that includes a third set of pillars and a fourth magnetoresistance element that includes a fourth set of pillars. The first set of pillars and the fourth set of pillars are disposed in a first matrix and the second set of pillars and the third set of pillars are disposed in a second matrix. The second magnetoresistance element is in series with the first magnetoresistance element, the third magnetoresistance element is in parallel with the first magnetoresistance element and the fourth magnetoresistance element is in series with the third magnetoresistance element.

In another aspect, a magnetic-field sensor includes a bridge. The bridge includes a first magnetoresistance element that includes a first set of pillars, a second magnetoresistance element that includes a second set of pillars, a third magnetoresistance element that includes a third set of pillars and a fourth magnetoresistance element that includes a fourth set of pillars. The first set of pillars and the fourth set of pillars are disposed in a first matrix and the second set of pillars and the third set of pillars are disposed in a second matrix. The second magnetoresistance element is in series with the first magnetoresistance element, the third magnetoresistance element is in parallel with the first magnetoresistance element and the fourth magnetoresistance element is in series with the third magnetoresistance element.

The foregoing features may be more fully understood from the following description of the drawings. The drawings aid in explaining and understanding the disclosed technology. Since it is often impractical or impossible to illustrate and describe every possible embodiment, the provided figures depict one or more illustrative embodiments. Accordingly, the figures are not intended to limit the scope of the broad concepts, systems and techniques described herein. Like numbers in the figures denote like elements.

FIG. 1A is a block diagram of an example of a bridge including tunnel magnetoresistance (TMR) elements with pillars;

FIG. 1B is a diagram of an example of a pillar of a TMR element;

FIG. 2 is a diagram of an example of a layout of a TMR element;

FIG. 3 is a diagram of another example of the layout of a TMR element;

FIG. 4 is a diagram of a further example of the layout of a TMR element;

FIG. 5 is a diagram of a still further example of the layout of a TMR element; and

FIG. 6 is a diagram of an example of a magnetic sensor having a bridge.

Described herein are techniques to form magnetoresistance elements using different layouts on a die (i.e., integrated circuit) that co-locate pillars of different magnetoresistance elements together. In one example, the magnetoresistance elements are tunnel magnetoresistance (TMR) elements. In one example, the pillars of one TMR element is interleaved with pillars from another TMR element. The techniques described herein may reduce mismatches and artifacts that may develop when TMR elements are used in bridges. The techniques described herein may also reduce laser pinning time, which, for example, may be reduced by a factor of two in most applications.

Referring to FIG. 1A , a bridge 10 includes at least four magnetoresistance elements (e.g., a tunnel magnetoresistance element (TMR) element 2 a , a TMR element 2 b , a TMR element 2 c and a TMR element 2 d ). The TMR elements 2 a , 2 b are in series with each other and the TMR elements 2 c , 2 d are in series with each other. The TMR elements 2 a , 2 b are in parallel with the TMR elements 2 c , 2 d . The TMR element 2 a includes a first set of pillars 12 , the TMR element 2 b includes a second set of pillars 14 , the TMR element 2 c includes a third set of pillars 16 and the TMR element 2 d includes a fourth set of pillars 18 . In one example, the TMR element 2 a may have the same reference direction as the TMR element 2 d , and the TMR element 2 b may have the same reference direction as the TMR element 2 c.

In one example, pillars in a set of pillars may be connected in series. In another example, pillars in a set of pillars may be connected in parallel. In a further example, some pillars in a set of pillars may be connected in parallel and other pillars may be connected in series.

Referring to FIG. 1B , an illustrative TMR element 100 can have a stack 102 of layers 106 , 110 , 114 , 118 , 122 , 126 , 128 , 132 indicative of one pillar of a multi-pillar TMR element. Generally, the layer 106 is a seed layer (e.g., a copper nickel (CuN) layer) with the layer 110 located on the seed layer 106 . The layer 110 includes platinum manganese (PtMn) or iridium manganese (IrMn), for example. The layer 114 is located on the layer 110 and the layer 118 is located on the layer 114 . In one example, the layer 114 includes cobalt iron (CoFe) and the layer 118 is a spacer layer and includes ruthenium (Ru). On the layer 118 , a magnesium oxide (MgO) layer 126 is sandwiched between two cobalt iron boron (CoFeB) layers 122 , 128 . A cap layer 132 (e.g., tantalum (Ta)) is located on the CoFeB layer 128 . The layer 114 is a single layer pinned layer that is magnetically coupled to the layer 110 . The physical mechanism that is coupling layers 110 and 114 together is sometimes called an exchange bias.

A free layer 130 includes the CoFeB layer 128 . In some examples, the free layer 130 may include an additional layer of nickel iron (NiFe) (not shown) and a thin layer of tantalum (not shown) between the CoFeB layer 128 and the NiFe layer.

It will be understood that a driving current running through the TMR element 100 runs through the layers of the stack, running between seed and cap layers 106 and 132 , i.e., perpendicular to a surface of a bottom electrode 104 . The TMR element 100 can have a maximum response axis that is parallel to the surface of the bottom electrode 104 and that is in a direction 129 , and also parallel to the magnetization direction of a reference layer 150 that includes the layer CoFeB 122 .

The TMR element 100 has a maximum response axis (maximum response to external fields) aligned with the arrow 129 , i.e., perpendicular to bias directions experienced by the free layer 130 , and parallel to magnetization of the reference layer 150 , notably pinned layer 122 . Also, in general, it is rotations of the magnetic direction of the free layer 130 caused by external magnetic fields that result in changes of resistance of the TMR element 100 , which may be due to a change in angle or a change in amplitude if an external bias is present because the sum vector of the external field and the bias is causing a change in the angle between the reference and free layers.

Referring to FIG. 2 , an example of a layout for the pillars is a layout 20 . The layout 20 includes a first matrix 21 and a second matrix 22 . In one example, a first matrix 21 is separated from the second matrix 22 by about 10 to 90 microns.

The first matrix 21 includes pillars from the first set of pillars 12 and the fourth set of pillars 18 . The first matrix 21 includes a set of columns 24 adjacent to a set of columns 25 . The set columns of columns 24 includes pillars from the first set of pillars 12 . The set columns of columns 25 includes pillars from the first set of pillars 18 .

The second matrix 22 includes pillars from the second set of pillars 14 and the third set of pillars 16 . The second matrix 22 includes a set of columns 26 adjacent to a set of columns 26 . The set columns of columns 26 includes pillars from the second set of pillars 14 . The set columns of columns 27 includes pillars from the third set of pillars 16 .

In one example, each pillar within a matrix is separated from the nearest pillar by about one to five microns.

Referring to FIG. 3 , another example of a layout for the pillars is a layout 30 . The layout 30 includes a first matrix 31 and a second matrix 32 . In one example, a first matrix 31 is separated from the second matrix 32 by about 10 to 90 microns.

The first matrix 31 includes a submatrix 34 a of pillars 12 (e.g., a pillar 12 a , a pillar 12 b , a pillar 12 c , a pillar 12 d ), a submatrix 34 b of pillars 12 (e.g., a pillar 12 e , a pillar 12 f , a pillar 12 g , a pillar 12 h ), a submatrix 36 a of pillars 18 (e.g., a pillar 18 a , a pillar 18 b , a pillar 18 c , a pillar 18 d ), and a submatrix 36 b of pillars 18 (e.g., a pillar 18 e , a pillar 18 f , a pillar 18 g , a pillar 18 h ). The submatrices 34 a , 34 b are interleaved with the submatrices 36 a , 36 b.

The second matrix 32 includes a submatrix 38 a of pillars 14 (e.g., a pillar 14 a , a pillar 14 b , a pillar 14 c , a pillar 14 d ), a submatrix 38 b of pillars 14 (e.g., a pillar 14 e , a pillar 14 f , a pillar 14 g , a pillar 14 h ), a submatrix 39 a of pillars 16 (e.g., a pillar 16 a , a pillar 16 b , a pillar 16 c , a pillar 16 d ), and a submatrix 39 b of pillars 16 (e.g., a pillar 16 e , a pillar 16 f , a pillar 16 g , a pillar 16 h ). The submatrices 38 a , 38 b are interleaved with the submatrices 39 a , 39 b.

In one example, each pillar within a matrix is separated from the nearest pillar by about one to five microns.

Referring to FIG. 4 , a further example of a layout for the pillars is a layout 40 . The layout 40 includes a first matrix 41 and a second matrix 42 . In one example, a first matrix 41 is separated from the second matrix 42 by about 10 to 90 microns.

The first matrix 41 includes a column 44 a of pillars 12 , a column 44 b of pillars 12 , a column 45 a of pillars 18 and a column 45 b of pillars 18 .

The columns 44 a , 44 b are interleaved with the columns 45 a , 45 b . In one particular example, the second matrix 42 includes columns alternating between columns having pillars 12 with columns having pillars 18 . For example, the column 45 a is between the columns 44 a , 44 b and the column 44 b is between the columns 45 a , 45 b.

The columns 47 a , 47 b are interleaved with the columns 48 a , 48 b . In one particular example, the second matrix 42 includes columns alternating between columns having pillars 14 with columns having pillars 16 . For example, the column 48 a is between the columns 47 a , 47 b and the column 47 b is between the columns 48 a , 48 b.

In one example, each pillar within a matrix is separated from the nearest pillar by about one to five microns.

Referring to FIG. 5 , a still further example of a layout for the pillars is a layout 50 . The layout 50 includes a first matrix 51 and a second matrix 52 . In one example, a first matrix 51 is separated from the second matrix 52 by about 10 to 90 microns.

In the first matrix 51 , the pillars 12 are interleaved with the pillars 18 . For example, pillars 12 are diagonally interleaved with pillars 18 .

In the second matrix 52 , the pillars 14 are interleaved with the pillars 16 . For example, pillars 14 are diagonally interleaved with pillars 16 .

In one example, each pillar within a matrix is separated from the nearest pillar by about one to five microns.

The techniques described herein are not limited to the specific embodiments described herein. In some embodiments, the matrices do not have to be completely filled with pillars. For example, the periphery of a matrix may include dummy structures. In other embodiments, the size of the matrices is not limited to 4×4 matrices. A matrix may be any size or shape of matrix, such as for example, 8×1 or 16×16, 2×2, 16×1 and so forth depending, for example, on the number of pillars, space on the IC and so forth.

The techniques described herein may be used in bridges for magnetic-field sensors. As used herein, the term “magnetic-field sensor” is used to describe a circuit that uses a magnetic-field sensing element, generally in combination with other circuits. Magnetic-field sensors are used in a variety of applications, including, but not limited to, the angle sensor that senses an angle of a direction of a magnetic field, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch that senses the proximity of a ferromagnetic object, a rotation detector that senses passing ferromagnetic articles, for example, magnetic domains of a ring magnet or a ferromagnetic target (e.g., gear teeth) where the magnetic-field sensor is used in combination with a back-biased or other magnet, and a magnetic-field sensor that senses a magnetic field density of a magnetic field.

Referring to FIG. 6 , an example magnetic field sensor 600 including a plurality of TMR element structures (here, four TMR element structures 602 , 604 , 606 , 608 ) is shown coupled in a bridge arrangement. The TMR element structures 602 , 604 , 606 , 608 , which can be the same as or similar to TMR element structures described in connection with figures above (e.g., FIGS. 2 to 5 ). It is understood that other configurations of the TMR element structures 602 , 604 , 606 , 608 are, of course, possible. Additionally, it is understood that other electronic components (not shown), for example, amplifiers, analog-to-digital converters (ADC), and processors, i.e., an electronic circuit, can be disposed over substrate 601 and coupled to one or more of the TMR element structures 602 , 604 , 606 , 608 , for example, to process signals (i.e., magnetic field signals) produced by the TMR element structures 602 , 604 , 606 , 608 .

In the illustrated embodiment, the magnetic field sensor 600 is disposed proximate to a moving magnetic object, for example, a ring magnet 610 having alternative north and south magnetic poles. The ring magnet 610 is subject to motion (e.g., rotation) and the TMR element structures 602 , 604 , 606 , 608 of the magnetic field sensor 600 may be oriented such that maximum response axes of the TMR element structures 602 , 604 , 606 , 608 are aligned with a magnetic field (e.g., an applied magnetic field) generated by the ring magnet 610 . In embodiments, the maximum responses axes of the TMR element structures 602 , 604 , 606 , 608 may also be aligned with a magnetic field (e.g., a local magnetic field) generated by a magnet (not shown) disposed proximate to or within the magnetic field sensor 600 . With such a back-biased magnet configuration, motion of the ring magnet 610 can result in variations of the magnetic field sensed by the TMR element structures 602 , 604 , 606 , 608 .

In embodiments, the TMR element structures 602 , 604 , 606 , 608 are driven by a voltage source and configured to generate one or more magnetic field signals in response to motion of the ring magnet 610 , e.g., in a first direction of motion and in a second direction of motion that is different than the first direction of motion. Additionally, in embodiments, one or more electronic components (e.g., ADC) (not shown) on the magnetic field sensor 600 are coupled to receive the magnetic fields signals and configured to generate an output signal indicative of position, proximity, speed and/or direction of motion of the ring magnet 610 , for example. In some embodiments, the ring magnet 610 is coupled to a target object, for example, a cam shaft in an engine, and a sensed speed of motion of the ring magnet 610 is indicative of a speed of motion of the target object. The output signal (e.g., an output voltage) of the magnetic field sensor 600 generally has a magnitude related to a magnitude of the magnetic field experienced by the TMR element structures 602 , 604 , 606 , 608 .

Additionally, in embodiments in which the TMR element structures 602 , 604 , 606 , 608 are provided as TMR element structures according to the disclosure (e.g., FIGS. 2 to 5 ), and the magnetic field sensor 600 includes electronic components (e.g., ADCs) coupled to receive magnetic field signals from the TMR element structures 602 , 604 , 606 , 608 and configured to generate the output signal of the magnetic field sensor 600 , operational requirements of the electronic components (e.g., so-called “front end electronics” or “signal processing electronics”) may, for example, be reduced in comparison to embodiments in which the magnetic field sensor 600 includes conventional magnetoresistance elements.

While the magnetic field sensor 600 is shown and described as a motion detector to motion rotation of the ring magnet 610 in the illustrated embodiment, it is understood that other magnetic field sensors, for example, current sensors or angle sensors, may include one or more of the TMR element structures according to the disclosure.

Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Various elements, which are described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. Other embodiments not specifically described herein are also within the scope of the following claims.